Mixed cellulose acetate-natural silk fabrics



Patented Feb. 4, 1936 umrao STATES MIXED OELLULOSE ACETATE-NATURAL SILK FABRICS Leo Wallerstein, Rowland A. Gale, and Thomas G. Hawley, Jr., New York, N. Y., assignors to Wallerstein Company, Inc., a corporation of New York No Drawing. Application April 26, 1934-,

Serial No. 722,507

1 Claim.

The present invention relates to silk fabrics and it particularly relates to improved novel fabrics composed of cellulose ester yarns and natural silk yarns.

It has been possible in the last several years to make high quality yarns from cellulose esters and ethers, and particularly from cellulose acetate. For many purposes it has been found desirable to combine these cellulose esters or cellulose acetate yarns, fibres, and materials with natural silk, particularly in the manufacture of chiffon or transparent velvets.

In forming these transparent velvets, the natural silk is usually employed in gum, that is, with the strands or fibres of the natural silk being encased or coated with the gum and after the fabric is formed it is necessary to treat'the fabric so as to remove this gum.

The degumming operation as a rule necessitates the employment of boiling solutions of high alkalinity containing soap. When such relatively high temperatures and alkalinities are employed, to degum the material silk contained in fabrics consisting of mixed cellulose acetate and natural silk in gum, the cellulose acetate frequently decreases in quality and is otherwise disadvantageously affected by the degumming solution.

For example, in some instances the cellulose acetate strands or fibres tend to melt or soften,

particularly at temperatures of about 180 F. and above. In the case-of velvets containing a cellulose acetate, an undesirable matting of the pile results from the treatment at high temperatures.

Also at about the same temperature under the alkaline conditions of the bath, the lustrous type of cellulose acetate would tend to be delustered, which was particularly objectionable in the case of manyfabrics, where the cellulose acetate was primarily utilized because of its high luster.

In addition at such alkalinities and temperatures on prolonged treatment, the cellulose acetate would also tend to saponify, thereby under going a chemical change which alters its dyeing aflinity. This change in dyeing aflinity is objectionable for three reasons. It may become impossible to obtain proper cross dyeing effects. It may be necessary to employ much higher concentrates of dyestufi' to obtain a given depth of shade, or it may be necessary to use an entirely different dyestufi. The dyeing afllnity of all fibres may not be changed, the same amounting giving rise to unevenness on dyeing.

For example, such a partly saponified cellulose acetate would tend to take up much greater quantitles of dyes and other finishing compounds and 5 was much less susceptible to careful control.

An object of the invention is to provide mixed cellulose acetate natural silk fabrics which may be most satisfactorily degummed under such conditions so as not to disadvantageously afiect 10 the cellulose acetate and particularly so as not to cause undesirable melting, delustering, and/or partial saponification of such cellulose acetate.

Other objects will appear during the course of the following specification. 15

According to the preferred embodiment of the present invention, it has been found desirable to prepare the natural silk, yarn or fibres, which are to be combined with the cellulose acetate fibres, so that the gum or best upon such natural 20 silk fibres may be most readily removed therefrom by relatively mild degumming operations which will only require such temperatures and alkalinities so as not to disadvantageously affect the desired qualities of the cellulose acetate ma- 5 terial.

According to the present invention, it has been found most suitable and desirable to resort to an impregnation of the natural silk in gum before twisting, knitting, and/or weaving, said impreg- 3 nation being performed with a proteolytic enzyme preparation under such conditions as notio degum the yarn and also as to leave the silk'in such a condition that it may be satisfactorily handled.

Among the preferred impregnating materials are liquid baths containing proteolytic enzyme preparations, such as those derived from the growth of certain types of bacteria, fungi, and also plant enzymes, such as papain.

In the preferred procedure, the natural silk 40 v and yarn in skein form issoaked in a bath of a temperature below 50 C.', said bath containing in solution or suspension, the proteolytic enzyme preparation, and also various suitable soaps and/or oils.

The natural silk, skein, or yarn, may be suspended in a soaking bath for a suflicient length of time to assure that the enzyme preparation and the other ingredients have thoroughly penetrated the raw silk fibres, and at all times the temperature and the pH should be so maintained that substantially no degumming action results.

The details of this soaking and impregnating Example 1-Sillc and cellulose acetate velvet The ground warp and filling of the fabric are made of natural silk which has beensuitably treated with proteolytic enzymes. The treated silk is made into threads of about 42 denier twisted about 65 turns per inch. The pile warp is made of cellulose acetate which has been twisted.

The natural silk threads which have been prepared from the enzyme treated silk are treatedwith water, for the-purpose of setting the twist. After drying, the threads are, woven together to make the fabric.

Degumming of the fabric is accomplished by immersing in a solution of soap of from 0.25 to 5% concentration. One half of the'soap may be substituted with anhydrous sodium sulflte. Temperatures varying from 110 F. to 180 F. may be used for this treatment. A gradually rising temperature may also be employed. The time required for the treatment is usually about two hours. Following this treatment, the fabric is rinsed either in water or a fresh soapsolution.

The degumming action in this case results from the combined actions of the enzyme and the soap or sodium sulfite; The enzyme may be said to activate the soap in a manner which enables the soap to dissolve the gum at temperatures much lower than would otherwise possible.

Example Milk-cellulose acetate crepe satin The warp consists of silk threads of cellulose acetate having only a very slight twist.

Thefillingismadeof5threadJapansilk twisted turns per inch, the silk in which prior to throwing has been treated with proteolytic enzymes. The threads so prepared are treated,

with steam to set the twist. In this case the high temperature of the steam destroys all or part of the enzyme remaining and the subsequent degumming is therefore not dependent upon further enzymic action.

The fabric is degummed by immersing it in soap solution from 2 .to 5% concentration at a temperature of to l". The time required is about 2 hours.

Ifordinarysilkhadbeenusedinstead ofthe specially prepared enzyme silk, a degumming period of about 8 hours would be, required.

The present application is a continuation in part of application Serial No. 806,286, filed April 19, 1932, and is similar in subject matter to copending applications Serial Nos. 722,504 to 722,506 and No. 722,508, all filed April 26,1934.

The present application is particularly directed to combination fabrics including cellulose acetate fibres and fibres of natural silk in gum.

What is claimed is: r A mixed cellulose acetate-natural silk fabric said natural silk being in .the gum, the natural silk fibres of said fabric being impregnated with and containing a proteolytic enzyme, without degumming, said fabric being capable of being degummed at a temperature of less than.185 F.

and at relatively low alkalimties to prevent in- 

